Yttrium-90 with a half-life of 64 hours is finding increasing use in the treatment of various forms of cancer. The National Cancer Institute has listed Y-90 as one of the top three radioactive isotopes being evaluated for use in cancer therapy. Medical researchers studying cancer treatment for the past five years have developed techniques using radioactive Y-90 labeled monoclonal antibodies to treat fatal adult T-cell leukemia. Others are using Y-90 labeled antibodies for studies of tumor therapy of ovarian, colon, and lymphatic cancers.
In order to be useful, the Y-90 must be exceptionally pure; free from other metal ions and free from Sr-90, an extremely toxic bone-seeking isotope. The typical therapeutic dose of Y-90 labeled monoclonal antibodies is the range of 100-300 millicuries of Y-90 per patient. Since an antibody is modified to contain only one molecule of chelating ligand per molecule of immunoprotein within the antibody, the total binding sites for metal ions are limited to about 7(10E-9) moles on 1 mg of chelate-modified immunoprotein. Since complexes of several metal ions including but not limited to zirconium(IV) and iron(III) form much stronger bonds than Y-90, specifications for chemical purity of Y-90 are necessarily strict for efficient labeling. (J. S. Wike et al. (Appl. Radiat. Isot. Vol. 41, No. 9, pp 861-865, Int. J. Radiat. Appl. Instrum. Part A, 1990, CHEMISTRY FOR COMMERCIAL SCALE PRODUCTION OF YTTRIUM-90 FOR MEDICAL RESEARCH), report producing multi-curie quantities of Y-90 having Sr-90/Y-90 separation factors of about 2(10E-6).
With the increased demand for Y-90, there is a need for a method capable of producing multi-curie quantities of Y-90 on a weekly basis with purities in terms of Sr-90/Y-90 separation factors less than 1(10E-8), and chemical impurities of unwanted cations including but not limited to iron, nickel, or a combination, wherein the chemical impurities are less than 10 ppm (parts per million) per curie of Y-90.